JPS5830397B2 - Electrolytic coloring method for aluminum or aluminum alloys - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrolytically coloring aluminum or an aluminum alloy (hereinafter referred to as aluminum) to a gold color.

Many methods for coloring aluminum have been reported, but the most representative ones include a method in which anodized aluminum film is immersed in an organic dye or inorganic compound solution (dying method), and aluminum alloy coloring. A method in which the film develops color during anodization (natural coloring method) by changing the composition of the anodized film or the composition of the electrolyte during anodization, and a method in which the anodic oxide film is electrolyzed with alternating current in a metal salt bath to inject metals or metal oxides into the pores of the film. Tokuko Sho 38-, which develops color by adsorbing it to
The method described in Japanese Patent No. 1715 (electrolytic coloring method) and the like have been put into practical use.

Among these, dyeing methods have particular difficulties such as weather resistance and uneven color due to variations in bath temperature and film thickness.On the other hand, natural coloring methods have There are problems such as difficulty in obtaining an alloy with a uniform composition, non-uniformity of color due to variations in coating film, variations in bath temperature, etc., and high cost.

Therefore, a method of coloring an anodic oxide film by electrolyzing it with alternating current in a metal salt bath is widely used.

By the way, several methods have been reported for obtaining a gold color using this method, but in all of them, the metals used were expensive or harmful, resulting in problems in terms of mass production, bath management, and pollution. There was a problem.

In addition, many gold colors had poor weather resistance.In view of the above circumstances, the present inventors have developed an electrolytic solution that is excellent in terms of weather resistance, bath management, mass production, uniform coloring, anti-pollution, cost, etc. After many years of research into gold coloring using coloring methods, we developed a method that has excellent weather resistance and is capable of electrolytic coloring to a uniform gold color. -26066 (Unexamined Japanese Patent Publication No. 51-1017
A patent application has been filed as No. 38).

The present inventors further conducted extensive research on electrolytic coloring to gold in an electrolytic bath containing tin salts, and found that weather resistance,
We have completed the method of the present invention by obtaining knowledge about the electrolytic coloring of aluminum to a gold color that provides satisfactory results in all aspects such as bath management, mass production, uniform coloring, anti-pollution, and cost. be.

That is, in the method of the present invention, anodized aluminum is heated in an electrolytic solution containing a metal salt using an alternating current waveform or a current waveform having an equivalent effect (hereinafter referred to as alternating current).
In the method of electrolytic coloring, the electrolytic solution is a stannous salt and sulfur is contained in the molecule, which is gradually decomposed in the solution or decomposed by undergoing an oxidation-reduction reaction due to alternating current. This method is characterized by the use of an electrolytic solution whose main component is a substance that releases sulfur (hereinafter referred to as a decomposable sulfur compound).This method satisfies all of the above-mentioned problems and turns aluminum into gold color. It has been found that electrolytic coloring is possible.

Incidentally, a method of using an electrolytic solution containing tin salt as a colored AC electrolyte for aluminum coated with an anodized film is known (Japanese Patent Publication No. 37823/1982), but this method does not require the electrolytic conditions or other electrolyte components. Even if adjusted, coloring to pale beige, olive, amber, red, and black was possible, but coloring to gold was impossible.

On the other hand, according to the present invention, if the electrolytic solution contains a stannous salt and a "degradable sulfur compound", it is possible to uniformly electrolytically color the product to a certain gold color.

To explain the present invention in detail, after degreasing aluminum, etching it, neutralizing it, washing it with water, removing smut, etc. using conventional methods as necessary, the aluminum is treated with an inorganic or organic acid.
For example, using sulfuric acid, oxalic acid, chromic acid, or the like as an electrolytic solution, anodic oxidation is performed according to a conventional method to form an anodic oxide film on the aluminum surface.

After carrying out necessary treatments such as washing with water, electrolytic coloring is carried out using an electrolytic solution containing at least one of a stannous salt and a ``decomposable sulfur compound'' added to the electrolytic bath.

Examples of stannous salts, which are one of the main components of the electrolytic solution used in the present invention, include stannous sulfate, stannous oxalate, and stannous chloride. It is fine as long as it provides the following.

The concentration of a stannous salt is 0 as the amount of stannous component in the salt.
．． 3SF/l (approx. 0.55t/l as stannous sulfate)
(0,55XSn/SnS 04 ==o, 3), which is about 0.5 f/l as stannous chloride) From the above, preferably considering the cost, the amount of the stannous component is 1
．． 0~2oy/l, (approx. 1.8~ as stannous sulfate)
35 t/l).

"Degradable sulfur compounds" include those belonging to thio compounds such as thiourea, thionyl chloride, thioglycolic acid, thiocyanic acid, thioacetic acid, thiocarbamic acid, etc., and their salts such as sodium, potassium, and ammonium;
or sulfur oxyacids such as sulfoxylic acid, dithionite, sulfurous acid, pyrosulfuric acid, pyrosulfite, dithionic acid, trithionic acid, tetrathionic acid, pentathionic acid, hexathionic acid, excluding sulfuric acid and its salts, or their sodium; There are salts such as potassium and ammonium, and sulfur halides such as sulfur dichloride and sulfur bromide.

The concentration of the degradable sulfur compound is approximately 0.08 f//l as the amount of sulfur component in its molecule (approximately 0.25 r/l as thioglycolic acid H80H2COOH).
0.25XS/H8CH3CO0H. os) or more, preferably 0.1 as the amount of sulfur component in the molecule
2-159/degree (thioglycolic acid H8CH2C0
0.43 to 54 gA) as OH.

At least one selected from the group of stannous salts and sulfur compounds mentioned above is added to the electrolytic solution, but usually an electrolyte component is added to make it conductive. In addition, a stannous antioxidant may be added.

Electrolytes to provide conductivity include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, and chromic acid, which are usually used in electrolytic coloring, as well as oxalic acid, acetic acid, propionic acid, formic acid, and tartaric acid. , organic acids such as citric acid, or their ammonium salts, amino salts, or imino salts.An aqueous solution of these is used as an electrolytic solution, and the above-mentioned compound is added thereto to obtain an electrolytic solution.

Furthermore, salts of the above-mentioned inorganic or organic acids of metals such as lithium, sodium, potassium, magnesium, and aluminum, which do not participate in color development, can also be added as electrolytes.

The concentration of these electrolytes added is about 3? / or more, preferably about 52 / or more (at saturated normal weight).

Adding an antioxidant to prevent the oxidation of stannous to stannic is often used in tin plating baths because tin salts are expensive and it is useful to keep the bath concentration constant. However, even if the electrolyte of the present invention contains an antioxidant (reducing agent)
The addition of is effective in obtaining a deep and uniform gold-colored colored film.

Examples of antioxidants include strong reducing substances such as hydrazine (hydrazine sulfate), hydroquinone, resorcinol, hydroxylamine, cresol sodium sulfonate, and L.
- ascorbic acid, ferrous salts of inorganic or organic acids,
Examples include weakly reducing substances such as formalin.

The stronger the reducing property is, the more suppressed the generation of stannic tin is, but as the amount added increases, the gold color becomes lighter, and when it exceeds about 51/2, it becomes almost uncolored.

On the other hand, even with weakly reducing formalin, the color becomes slightly lighter, but with L-ascorbic acid, ferrous salts of inorganic acids, or organic acids, there is no change in density or color tone at all.

Therefore, when adding an antioxidant, weakly reducing substances, especially L-ascorbic acid and ferrous salts are preferred;
5 for strongly reducing substances? / must be used below.

The precipitates produced by the conventional alternating current electrolytic coloring method in a tin bath are metallic tin,
It is assumed that tin oxide or reduced tin hydroxide is produced, but in the method of the present invention, it seems that a large amount of tin sulfide is produced from "degradable sulfur compounds", and this sulfur It is thought that the color of tin (gold) is added to give the appearance of a gold color.

The aluminum used in the present invention is not particularly limited as long as it can be anodized.

The anodic oxide film electrolytically colored as described above is subjected to a sealing treatment using boiling water, chemicals, pressurized steam, or the like, if necessary.

After carrying out this sealing treatment, or without sealing, the surface of the housing may be further protected by dip coating or electrodeposition coating with a resin paint, if necessary.

Next, the present invention will be explained in more detail by giving examples.

Conditions for primary electrolysis, polar ratio of electrolytic coloring, bath temperature,
Conditions such as voltage are specific examples and are not limited thereto.

Example 1 An extruded aluminum profile A-60638, T-5 that had been degreased, etched, and smutted by a conventional method was heated to 17.5 mm.
An anode was immersed in a w/v% sulfuric acid aqueous solution, and a current density of 1.
Electricity was applied at room temperature for 35 minutes at 25 A/dm'' (voltage of about 15 V) to form an anodic oxide film of about 15 μm on the surface.

Next, this was washed with water.

Next, the length is 300rrrm, the width is 100mm, and the height is 150mm.
rrvn container was used as a device for coloring electrolysis, a carbon counter electrode was placed at one end of the container, and the length was 150 and the width was 70 Cr.
r1, thickness 1.3 mm, the distance between the poles is about 280
When immersed in an electrolytic solution having the following composition at a bath temperature of 20°C and subjected to AC electrolysis for 4 minutes at an applied voltage of 12 V, both the counter electrode surface and the non-counter electrode surface of the aluminum extruded shape were uniform with no unevenness. A golden colored film was obtained.

Electrolyte composition: stannous sulfate 49/sulfuric acid 401/sodium trithionate 1, Of/l After washing the colored film thus obtained with water, 5 kg
/crA pressurized steam for 30 minutes and accelerated weathering test for 3,000 hours with a weather meter, no abnormalities were observed, and the material was not tested after heating at 200℃ for 2 hours. There was no change in coloration.

Furthermore, there were no abnormalities in the Cath test after 16 hours, confirming that the product had sufficient performance as an exterior material.

Comparative Example 1 After forming a 15 μm anodic oxide film in the same manner as in Example 1, electrolytic coloring was performed under the same conditions as in Example 1 except that only the coloring electrolyte composition was changed to the following composition. The profile became a light beige color, and the non-opposite surface was colored slightly lighter than the counter electrode surface.

Electrolyte composition: stannous sulfate 41/ and sulfuric acid 401/ Comparative Example 2 After anodizing in the same manner as in Example 1, an electrolyte with the same composition as in Example 1 was added with a stannous oxidation inhibitor. 10 tons each of hydrazine sulfate and cresol sulfonic acid for the purpose
When electrolytic coloring was carried out under the same conditions as in Example 1 using an electrolytic solution to which /l was added, both films became extremely pale gold colors, which were comparable to uncolored films.

Comparative Example 3 For the same purpose as Comparative Example 2, a lot/lot of formalin 37 polyaqueous solution, L-ascorbic acid, and ferrous sulfate were added to an electrolytic solution having the same composition as in Example 1, and electrolysis was carried out in the same manner as in Comparative Example 2. When coloring was carried out, the formalin color was slightly lighter, but it was a fairly deep gold color, and the L-ascorbic acid and ferrous sulfate had exactly the same depth and color tone as the gold color obtained in Example 1. Met.

Example 2 Extruded aluminum profile A-606 in the same manner as Example 1
3S, T-5 at a current density of 1. OA/drr? Electrolysis was carried out for 33 minutes to form a 10 μm anodic oxide film, and when electrolytic coloring was carried out under the same electrolytic coloring conditions as in Example 1 using an electrolytic solution with the following composition, both the counter electrode surface and the non-counter electrode surface were uniform. A gold colored film was obtained.

Electrolyte composition: stannous sulfate 4 g/l, tetrathionic acid 0.5 r/l, sodium thioglycolic acid 0.5 g/l formalin 51/1 (37φ aqueous solution) sulfuric acid 301/l Example 3 Example 1 After forming a 15 um anodic oxide film in the same manner, electrolytic coloring was carried out under the same conditions as in Example 1, except that only the composition of the colored electrolyte was changed to the composition shown below. A uniform dark gold colored film was obtained on both the non-counter electrode surface.

Electrolyte composition: stannous sulfate 3 g/l thiourea 251/l ammonium sulfate 251/l glyconic acid 10 ? /l Ammonium Example 4 When electrolytic coloring was carried out in the same manner as in Example 3 using an electrolytic solution having the following composition, a uniform pale gold-colored colored film was obtained on both the counter electrode surface and the non-counter electrode surface.

Electrolyte composition: stannous chloride 14/l, thionyl chloride 0.4 f/l, formalin 3 g/1 (37% aqueous solution) sulfuric acid 30ff/ammonium sulfate 20? Example 5 When electrolytic coloring was carried out in the same manner as in Example 3 using an electrolytic solution having the following composition, a uniform slightly pale gold-colored colored film was obtained on both the counter electrode surface and the non-counter electrode surface.

Electrolyte composition: 101/l of stannous sulfate, 32/l of cyclic dithionic acid, 10/l of sodium acetic acid, 51/l of ferrous sulfate (7 hydrate) Example 6 Electrolysis with the following composition in the same manner as in Example 3. When electrolytic coloring was performed using the solution, a uniform gold-colored colored film was obtained on both the counter electrode surface and the non-counter electrode surface.

Electrolyte composition: stannous sulfate 1.59 g/l, trithionic acid 0.4 g/l, sodium sulfuric acid 45 f/1, formalin Is'/A (37 multi-aqueous solution) ammonium sulfate 30 g/l, gold color of Examples 2 to 6 The colored extruded aluminum shape is washed with water, and after washing with warm water, it is electrocoated to JISA-4.
As a result of conducting an accelerated weathering test, an alkali resistance test, an acid resistance test, and an adhesion test as specified in 706, results were obtained that fully satisfied the conditions specified in JIB.

Claims (1)

[Claims] 1 Aluminum or aluminum alloy subjected to anodizing treatment is exposed to alternating current in an electrolyte containing metal salts! Or, in the method of electrolytic coloring using a current waveform that has an equivalent effect, the electrolyte contains a tin salt and a sulfur atom in the molecule, which gradually decomposes in the solution or undergoes an oxidation-reduction reaction by alternating current. 1. A method for electrolytic coloring of aluminum or aluminum alloys, which is characterized by using an electrolytic solution whose main component is a substance that releases sulfur when it is decomposed.